In Fox's several years old _Biology and Diseases of the Ferret_ the
author of that section (in this chapter, Fox) goes into cataracts on
page 311 and 312, mentioning metabolic, hereditary, congenital,
infectious, and traumatic causes. He mentions that many ferrets have
slowly acquired cataracts. I get further confused when he mentions
retinal degeneration as a result (rather than a cause)of luxated
cataracts, so really need more information. Later he goes into diet
possibly playing an important factor for ferrets and pointed out,
among other things that at least one form of mink diet seemed to
possibly be quite prone to this result.

Quesenberry and Hillyer's _Ferrets, Rabbits, and Rodents_ is also a
few years old. They mention Vitamin A deficiency as a cause of
cataracts and two other occular pathologies, night blindness and
conjunctivitis, and riboflavin deficiency as a cause of corneal
vascularization). For cataracts they also mention heredity, diet,
and idiopathic causes, and recommend that ferrets with cataracts not
be bred due the genetic factor. Ferrets with mature cataracts may
squint; I can see you all examining your ferrets (LOL!). There can
be inflammation complications from cataracts that require long term
treatment, they write, and they also say that there have been
successful cataract surgeries in ferrets though lenses can not be
placed due to size. Their mention of retinal degeneration does not
give it as a cause or result of cataracts, though it does mention a
shared dietary cause, and they also advise that these individuals not
be bred due to the hereditary component.

Purcell's _Essentials of Ferrets_ also mentions the hereditary
component, aging, and the possibility of nutritional or
environmental factors. Like Q&H she goes into the complications that
can occur and how to handle them. In her thrid paragraph on the
topic Dr. Purcell mentions that cataracts can cause lens luxation
[dislocation], but that retinal atrophy is a more common cause. The
signs of this are those of acute eye pain with anorexia, pawing of
eye, or swelling possible. Surgery sounds as if it is often needed,
though there is a medical approach which may need to be repeated in
short order.